Wednesday, June 29, 2016

Sugarcane Aphid on the Texas High Plains; So Far a No-show

Given that we know sugarcane aphid overwintered as far north as Plainview, and that it was found on Johnsongrass in Lubbock County in early May, the question we are most frequently asked lately is, "Why don't we have sugarcane aphids yet?"

That is a good question, and I wish I could be totally certain of the answer. I suspect that our beneficial insects wiped out the overwintering aphids. We had extremely high numbers of ladybugs, syrphid flies and the other predators that went in to overwintering last year after feasting on sugarcane aphids. In what should be considered to be good news, we also had fairly heavy aphid numbers in wheat this spring, but not enough to do significant economic harm. But these wheat aphids, which were not sugarcane aphids, provided food for our early season beneficial insects, which in turn were available to start munching on the overwintering sugarcane aphids in the area. This is just conjecture on my part, but it is the simplest explanation of why sugarcane aphid was here in the early season and is now gone.

The next most common question we are getting is, "When will the aphids arrive?" Of course no one knows the answer, but later is better, and growers who planted early are seeing a benefit from that practice. Last year the first sugarcane aphids found on the High Plains were discovered in Lubbock County on June 27th, and within three weeks we were scrambling to get fields sprayed. I think that last year we had some colonies beginning to build locally in late June, but, given the wide area infested a few weeks later, it is most probable that one or more flights of winged aphids came up from the south on wind or storm events. This year we probably do have some small pockets of sugarcane aphids locally. The good news is that aphids are not extremely numerous on the Gulf Coast and in the Hill Country. Our colleagues south and east of here are reporting that they have only light to moderate infestations (although some fields required treatment). They are also saying that beneficial insects are catching up to the aphid populations and decimating them. This is means there will be fewer aphids traveling on the winds and landing on our front door. If we have fewer aphids colonizing our plants then the beneficial insects we have in the system will have a better chance of suppressing those that do arrive.

I wish I could predict what will happen in the next few weeks, but of course I can't. If you find sugarcane aphids in your fields then please give us a call. The telephone numbers for your High Plains IPM Agents and Extension Entomologists are listed here. We sincerely appreciate people who take the time to call and report pest problems.